When I was but a wee nerdling, I took a course taught by a grizzled veteran of the computer industry. I can no longer remember the subject matter of the course, but I do remember that at one point he referred to the main players in the computer business as "IBM and D'BUNCH". D'BUNCH were DEC, Burroughs, Univac, NCR, Control Data, and Honeywell. (And yes, I had to resort to Wikipedia to remember all these names.)
The moral of the story? Computer manufacturers come and go, but IBM remaineth eternal, apparently.
Dating myself even more, in the early part of my career I used machines made by the first 3 of these. The Univac had the distinction of having the most obtuse, unwieldy, difficult-to-use OS I have ever encountered. DEC, in contrast, had the best OS (of proprietary ones, that is - *nix blows 'em all away).
14 hours ago